Thursday, December 7, 2023

Digging into the potential for a holiday-season storm event on Saturday

As we approach another busy holiday season weekend, the threat of rain and thunderstorms is threatening to put a damper on at least half of it. The fact that there is some potential for strong to severe storms reminds us that it is not just the holiday season, but also still secondary severe weather season in Dixie Alley. Let's take a look at what to expect for those with Saturday shopping, decorating, baking, or other "tis the season" plans.

Priming the atmospheric pump

A December warm-up has commenced. High temperatures were back into the lower 60s Thursday afternoon and slightly warmer conditions are on tap Friday, despite more cloud cover, as southerly flow has become established across the region. That will also lead to milder overnight conditions heading towards the weekend, as well as rising dewpoints - a sign that moisture is increasing. 

Friday will be "pump primer day" as dewpoints steadily climb into the 50s on gusty south wind, heading towards 60 degrees by Saturday morning. Cloud cover will also thicken up Friday as upper level moisture also increases. A few sprinkles or a brief afternoon shower are possible, though most stay dry before sunset. By Friday evening, conditions will be very mild with after-dusk temperatures near 60 and southerly wind gusts to 25 mph. The chance of showers climbs in the evening as well, so though it will be comfortable, raindrops will be scattered around if you are going to holiday parties/events or the Grizzlies matchup with the Timberwolves downtown.

Forecast dewpoints from Friday sunrise through midnight. Southerly flow will bring increasing moisture to the region on Friday. (WeatherBell)

Saturday: a wash-out at a minimum

By Saturday morning, the cold front that will likely disrupt outdoor events during the day will have made its across AR a chunk of Arkansas. Where exactly it will be is still TBD, but it is safe to say it will be to our west, which puts areas from Louisiana and southern AR into the Mississippi Delta, and potentially the Memphis metro, in a zone of unsettled conditions. As low pressure moves along the front, it will bring more unstable air into this "zone of unsettled-ness," juxtaposed with increasing wind aloft that could serve to strengthen any storms that can form in warm, unstable air. We do expect to see thunderstorms embedded within areas of heavy rain during the day Saturday, but the degree to which they become "strong" or even severe, is a tricky question, even if you were to forget that it is indeed December. 

Surface weather map on Saturday at 6am (NWS/WPC)

What is unknown as of Thursday evening is how much storm fuel (aka, instability) will be present over our area and when exactly the front will move through, which will bring an abrupt end to the severe weather chances. While the wind energy over the Mid-South seems sufficient to support a low-end severe weather threat, instability is likely to be more prolific to our south. The later the front arrives (i.e., late afternoon), the better the chances are that we see scattered strong to severe wind gusts. If it seeps southeast into the metro earlier in the day, it will shove the unstable air to our east and we'll be in for a wet, but not too stormy, day. 

Most computer model solutions right now favor a mid-afternoon frontal passage. Thus, the Storm Prediction Center currently has their level 2 ("Slight") severe weather risk area extending over the metro (see above). Should we get strong storms, they would be most likely in the afternoon hours and damaging wind would be the greatest concern, besides heavy rain. Tornado and hail threats appear fairly low. In any case, rain looks to continue through the evening hours and could be heavy at times, as temperatures begin their plummet from the upper 60s towards the upper 30s by Sunday morning. It won't be a pleasant evening by any stretch.

Cold winter air arrives

Behind the front, cool high pressure quickly builds in. In fact, it will be downright cold on Sunday, despite abundant sunshine. Wind chills in the morning will be in the 20s and high temperatures in the afternoon only in the mid 40s! A great day to sip a warm beverage indoors and gaze outside at the seemingly beautiful day. The rest of next week is dominated by cool high pressure. Rain chances don't reappear until the following weekend, natch, with highs generally in the mid 50s and lows in the 30s. 

Erik Proseus
MWN Meteorologist

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1 comment:

Anonymous said...

Thank you, Erik!